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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I'm having issues with my lennox g16 conservator III. This

Customer Question

I'm having issues with my lennox g16 conservator III. This started at the end of last year. The furnace would run to desired temp and turn off. When it came time to run again, the inductor fan would start and then you would heAR the clicking but the furnace wouldn't light, but the fan get running. If you turned it off for 30 seconds and then turned it back on it would work. This happened last spring so it got warm and I forgot about it. When we needed the furnace this fall it worked fine for about two weeks, then the same problem. You had to turn it off then it would light. Now the fan starts but there isn't even any clicking.
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Assuming you don't have a blocked vent this could be caused by an issue with the draft pressure switch. The draft switch has (2) small vacuum tubing connected to it and it's located at the top left of the burner compartment. Once the inducer fan gets going try jumping the 2 leads on the draft switch. Tell me what happens.

Customer: replied 1 year ago.
Absolutely nothing
Expert:  Rick replied 1 year ago.

Try jumping the leads on the LIMIT side of the fan/limit control. Be sure to just jump the leads on the right side of the control (which are 24 volt). The left (fan) side is line voltage.

Customer: replied 1 year ago.
Would the right side be the side with wire coming from pressure switch?
Expert:  Rick replied 1 year ago.

The limit is wired in series with the pressure switch

Customer: replied 1 year ago.
Expert:  Rick replied 1 year ago.

You probably have a problem with the ignition controller but it's so old I don't know if a replacement is available or what that replacement might be. I'm going to open this backup to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.

Expert:  Rick replied 1 year ago.

Something else came to mind that you can also check if you have a meter. Check for 24 volts AC at the transformer (my diagram shows blue & yellow leads). Also some models have a fuse or circuit breaker in the control box.

Customer: replied 1 year ago.
I think your diagram is different from my furnace. Is it the transformer under where my thermostat wires hook into the control box? Also I put my meter on the terminal in the limit switch that goes to the pressure switch and get 24v.
Customer: replied 1 year ago.
I also put my meter to both terminals of the pressure switch and get 24v on each side
Expert:  Rick replied 1 year ago.

If you have 24 volts at the switch hen the transformer is working OK. It still looks like you have an ignition control problem.

Customer: replied 1 year ago.
I had to call a tech I couldn't wait for hours it is 20 degrees here.
Expert:  Rick replied 1 year ago.

I understand. You weren't likely to find the control anyway except perhaps online. You tech might have local access.